1. Field of the Invention
The present invention relates to an opto-electric hybrid board which includes an optical waveguide unit and an electric circuit unit having an optical element mounted thereon, and a manufacturing method therefor.
2. Description of the Related Art
In recent electronic devices or the like, as the amount of transmission information increases, in addition to electric wiring, optical wiring is adopted. More specifically, an opto-electric hybrid board including an electric circuit unit in which an optical element such as a light-emitting element for converting an electrical signal into an optical signal or a light-receiving element for converting an optical signal into an electrical signal is mounted on an electric circuit board having electric wiring formed thereon, and an optical waveguide unit in which an optical waveguide as optical wiring for transmitting the optical signal is formed is incorporated in the electronic device or the like.
As the above-mentioned opto-electric hybrid board, for example, as illustrated in FIG. 15, there is proposed an opto-electric hybrid board in which an optical waveguide unit W0 is provided on a rear surface side of an optical element mounting surface of an electric circuit unit E0 so as to be parallel to the electric circuit unit E0 (see, for example, JP-A1-2010-192883). In an opto-electric hybrid board of this type, one end surface 52a of a core 52 (optical wiring) of the optical waveguide unit W0 is formed as an inclined surface which is inclined 45°, and the inclined surface of the core is formed into a light reflecting surface. Specifically, the one end surface (inclined surface) 52a of the core 52 reflects light to change an optical path by 90° so that the light may be transmitted between the core 52 and an optical element 10 (see a dot-and-dash line L in the figure). Note that, in FIG. 15, the reference numeral 51 denotes an undercladding layer, the reference numeral 53 denotes an overcladding layer, and the reference numeral 61 denotes a through hole for the optical path.
In the opto-electric hybrid board, light which is emitted from the light-emitting element is required to be reflected by the one end surface 52a (inclined surface) of the core 52 of the optical waveguide unit W0, and light which exits the other end surface (light exit) of the core 52 is required to be received by the light-receiving element. Therefore, it is necessary that the optical element (the light-emitting element or the light-receiving element) 10 and the core 52 be aligned with each other.
Accordingly, methods of aligning the optical element and the core are conventionally proposed. In an exemplary method, an optical waveguide unit is fixed and, in a state in which light is emitted from a light-emitting element to one end surface (light entrance) of a core of the optical waveguide unit while the location of the light-emitting element is changed, the intensity of light which exits from the other end surface (light exit) of the core is monitored, and the location at which the intensity becomes the highest is determined as the alignment location (see JP-A1-HEI5 (1993)-196831). In another exemplary method, a connector having holes for locating formed therein is attached to an optical waveguide unit, pins for locating, which fit into the holes, are attached to an electric circuit unit, and, by fitting the pins into the holes, respectively, an optical element and a core of the optical waveguide unit are automatically aligned (see JP-A1-2009-223063).
However, in the aligning method described in JP-A1-HEI5 (1993)-196831 above, although alignment with high accuracy is possible, it takes time and effort, and thus, the method lacks mass-productivity. Further, in the aligning method described in JP-A1-2009-223063 above, although position adjustment may be carried out in a simple method of fitting the pins into the holes, respectively, not only dimensional deviations are caused when the connector and the pins are respectively manufactured but also misalignment of the attachment location of the connector with respect to the optical waveguide unit, misalignment of the attachment location of the pins for locating with respect to the electric circuit unit, and the like are caused. Accumulation of those dimensional deviations and misalignments lowers the accuracy of the alignment. If enhancement of the accuracy of the alignment is attempted, control of the dimensional accuracy is necessary so that the dimensional deviations and misalignments are not caused, and thus the cost increases and the method lacks mass-productivity.
In addition, as described above, in the opto-electric hybrid board in which the optical waveguide unit is provided on the rear surface side of the optical element mounting surface of the electric circuit unit so as to be in parallel to the electric circuit unit as in JP-A1-2010-192883 above, it is necessary to form the one end surface of the core as an inclined surface (light reflecting surface) which forms an angle of 45° with accuracy to change the optical path by 90° so that light may be transmitted between the core and the optical element. However, this lacks productivity because it is necessary to form the above-mentioned inclined surface.